Egoism describes a selfish person. They may have received a raise at work, and instead of helping to pay for a family member's operation, they blow it all on things they don't even need, which is the type of person who is more interested in themselves and no other people.
These are the people who will have a conversation with someone to wait for the person to stop talking to talk. They think that what they have to say is more important. Egotism, on the other hand, describes someone insensitive. They do not care about other people's emotions, and they may even lack compassion. This person is more concerned with themselves and their needs.
Someone may be noticeably upset, and instead of asking if the person is okay, they either ignore the person without a second thought or talk about themselves. They may also have trouble relating to others or do not understand their point of view.